Cyanobacterial biocrust induction: A comprehensive review on a soil rehabilitation-effective biotechnology

The use of cyanobacteria as soil inoculants is a very promising biotechnological approach that is receiving increasing scientific attention for its potential for soil degradation control. Inoculation of selected cyanobacterial strains has shown the ability to significantly improve the physicochemical properties of degrading soils in different environmental settings and on soils with different textures. First, inoculation of cyanobacteria promotes sediment stability against wind and water erosive action. Second, successful establishment of cyanobacteria in the target soil can lead to the development of self-sustaining microbial communities known as biocrusts, which are recognized as ecosystem engineers in drylands. Due to their important natural ecological role, the artificial onset of biocrusts contributes to the improvement of ecosystem status. Advances in cyanobacteria inoculation studies both at laboratory and field scale demonstrated that the technology can represent a valuable tool for rehabilitating even hyper-arid soils subjected to severe abiotic conditions.This review provides an overview of the state of the art of cyanobacteria inoculation, highlighting the most recent published results on the use of cyanobacteria to address soil rehabilitation. At the same time, it examines the remaining knowledge gaps that currently limit the potential of the technology and its applicability in different environmental settings. We found that three main aspects require further investigation: the need to standardize and optimize inoculation protocols in order to maximize the percentage of success in soil rehabilitation, the need to clearly define benchmarks to validly assess inoculation effects and ease the comparison between different studies, and the need to better understand and control the influence of environmental factors on inoculation success/failure. The improvement of these aspects of the technology are fundamental for its optimization and its applicability on a wide scale.